VANDENBERG AIR FORCE BASE -- Streaking back into action after a two-and-a-half-year hiatus, a Delta 2 rocket launched NASA's Orbiting Carbon Observatory No. 2 this morning to watch the Earth breathe from space.

The Delta 2 blasts off from foggy pad. Credit: Tim Dodd

The two stage-launcher ignited its Aerojet Rocketdyne RS-27A main engine and three ATK strap-on boosters at 2:56 a.m. PDT (5:56 a.m. EDT) to depart a very foggy Space Launch Complex 2 at Vandenberg Air Force Base in California.

The solid burned for a minute, then waited another 40 seconds to clear offshore oil platforms before jettisoning some 20 miles in altitude. The vehicle had shed half of its 165-ton liftoff weight within the first two minutes of flight.

The first stage accelerated the vehicle to an altitude of 70 miles before separating and letting the hypergolic second stage light as the nose cone jettisoned at 11,000 mph some five minutes after launch.

The shroud separation came as a sigh of relief to the engineers and scientists on the $468 million mission after that event went horribly wrong and downed the OCO 1 satellite during its launch five years ago.

But there was plenty still left in the Delta flight. Flying southward, the rocket settled into a parking orbit within 10-and-a-half minutes of liftoff, flying in a 115-by-450-mile orbit for 40 minutes and cruising above the South Pole.

Then came a second firing, a 12-second burn by the Aerojet Rocketdyne engine, that brought the orbit to a more circular one and released the observatory 56 minutes into flight in a 426-by-434-mile orbit tilted 98.2 degrees to the equator.

The Delta 2 blasts off from foggy pad. Credit: Tim Dodd

It was the 150th successful Delta 2 launch in a quarter-century of flight and the 97th in a row for the venerable rocket. OCO 2 became the 228th primary payload put into space by a Delta 2.

"I do dearly love this rocket," said NASA launch director Tim Dunn. "We couldn't be happier to be back in the Delta 2 business."

The Orbiting Carbon Observatory before it and OCO 2 now were designed to study natural and man-made carbon dioxide emission and absorption to help scientists assess how the greenhouse gas is contributing to global warming.

"The most important aspect about the OCO 2 mission is that we're going to be able to produce data and make it available to the scientists (and) the general public so that we can have an opportunity to better understand the processes that are driving the global climate change and be better stewards of Mother Earth," said Ralph Basilio, OCO 2 project manager with NASA's Jet Propulsion Laboratory in Pasadena, California.

"We know what we emit when we burn fossil fuels, we know how much shows up in the atmosphere and about half of it doesn't stay in the atmosphere each year -- it goes into the land and the oceans. We are trying to figure out where that is and how those processes are happening," said Annmarie Eldering, OCO 2 deputy project scientist at JPL.

"We'll see, every two weeks or so, how much carbon dioxide there is left in the atmosphere. We call this watching the planet breathe," said PJ Guske, mission operations systems manager of OCO 2.

"These are things we clearly need to understand if we want to manage the carbon dioxide in our atmosphere," David Crisp, OCO 2 science team leader.

"As we launch OCO 2, the data we provide will help our decision-makers at the local and federal levels to be better equipped to understand carbon dioxide's role in climate change, because OCO 2 will be measuring this greenhouse (gas) globally and understanding and providing new insight into where and how the carbon dioxide is moving into and out of the atmosphere," Edwards said.

An artist's concept of OCO 2. Credit: NASA/JPL-Caltech

NASA won approval to build a replacement satellite and buy a more mature, expensive rocket to launch OCO 2 given the criticality that the data promises to provide.

"Due to the importance of this mission to the scientific community and to society, NASA was given permission to rebuild the satellite," Edwards said.

"The loss of the original OCO mission was a tremendous heartbreak for all of us. It was truly devastating. It was the true sense of loss," said Basilio.

"We are excited about this golden opportunity to be able to finally complete some unfinished business. And this launch doesn't signal the end of a road, but it's the next step to a very important mission."

But the two spacecraft aren't identical clones.

"It's not what we lovingly call a carbon copy of OCO, in that there were some necessary changes that had to be made, primarily due -- almost exclusively due -- to parts obsolescence," Basilio said.

OCO 2 will undergo an initial systems checkout, then use its hydrazine thrusters to ascent into the so-called A-train constellation of Earth-watching satellites where it will be the lead spacecraft 438 miles up. After an instrument exam period, science operations will begin in about 6 to 8 weeks.

Standing seven feet tall by three feet wide and a 29-foot wingspan with the solar arrays deployed, the 999-pound, hexagon-shaped satellite features one science instrument, a three-channel grating spectrometer, to perform its mission.

"With that one instrument, we're going to collect hundreds of thousands of measurements each day, which then will provide a global description of carbon dioxide in the atmosphere. It is going to be an unprecedented level of coverage and resolution, something we've not seen before with previous spacecraft," Edwards said.

The Delta 2 rocket revealed for launch. Credit: Walter Scriptunas II SEE MORE IMAGES

A single orbit will last 99 minutes and the globe will be covered every 16 days, collecting 8 million measurements in each mapping cycle. That global perspective is what makes OCO 2 special in tracking seasonal and yearly viables to carbon dioxide.

"To date, much of what we know comes from a few extremely important ground-based observations," said Mike Gunson, OCO 2 project scientist at JPL.

Scientists have a number of unanswered questions about this key greenhouse gas. Among them that OCO 2 will tackle:

• What natural processes dominate the absorption of carbon dioxide from human emissions?
• Will those processes continue to limit increases in atmospheric carbon dioxide in the future, as they do now? Or will they stop or even reverse and accelerate the atmospheric increases?
• Is the "missing" carbon dioxide being absorbed primarily by land or by the ocean and in what proportions?
• Which terrestrial ecosystems absorb more than others?
• Why does the increase in atmospheric carbon dioxide vary from one year to the next even though the emission rates increase uniformly?
• How will carbon dioxide sinks respond to changes in Earth's climate or land use?
• What are the processes controlling the rate at which carbon dioxide is building up in Earth’s atmosphere? That rate is currently estimated at two to three parts per million by volume per year, or as much as a half percent per year.
• Where are the sources of carbon dioxide?
• What is the geographic distribution and quantity of carbon dioxide emitted through both fossil fuel combustion and less well understood sources, such as ocean outgassing, deforestation, fires and biomass burning? How does this distribution change over time?

"Right now, we have a 60-year data record that shows that CO2 concentration levels have increased by about 100 parts per million, or about 25 to 30 percent, in the last 60 years. But only about half of that carbon dioxide that's omitted through human activity, like fossil fuel emissions, stays in the atmosphere," Basilio said.

"The other half is being absorbed by the oceans and by plants on the land. We would like to identify where these sinks, or absorbers, of CO2 are because we would like to get a better understanding of what's going to happen over time.

"Are these sinks going to become less efficient? Are they going to become saturated? Does that mean more carbon dioxide stays in the atmosphere? What happens when more carbon dioxide stays in the atmosphere? Is that going to further accelerate the global climate change process?

"These are only but a few of the basic science questions that we hope to be able to answer with the OCO 2 mission," Basilio said.